Soft conducting polymer polypyrrole actuation based on poly(N-isopropylacrylamide) hydrogels

Abstract

The conducting polymer, polypyrrole (PPy), has been widely studied as electrochemical actuators due to their electrochemical stability, fast actuation and high strains. However, conducting polymers films are rigid and brittle, which limit their applications. Conducting polymer hydrogel composites take advantage of hydrogels’ elastic properties and extend their use to biological applications, implants and flexible sensor applications. We systematically investigated the out-of-plane actuation of poly(N-isopropylacrylamide) (pNIPAM) hydrogel by utilising the redox properties of a PPy film. We assess the PPy film growth with different sized dopants and find that PPy-dodecylbenzene sulfonate (DBS) films exhibited the largest strain (∼20 %) with a cation-driven actuation. We show that the Young's Modulus of the composite hydrogel was ∼10 kPa, which remained constant regardless of the redox state of PPy. Furthermore, we show that the PPy-DBS film grown in the pNIPAM hydrogel exhibits more than x2 the actuation of the PPy-DBS film alone by electrochemical switching of the redox state. This system has potential applications for soft actuators, controlling ion flux, drug delivery or applying electrical stimuli for cell culture studies.